java关联数组之类的东西不止一种数据类型

Question

imagine this: DataTypeForConfigs config with String keys, but values of either String , Integer , or Boolean , in Java, JSON can do that, but I'm making a format That goes along the lines of:

number "coolness" is 9001 means int coolness = 9001;

It's method is: Read line, read each word, think what to make of it, set it to a Variable within it's reach

Also: what would happen if another thing had its own place to put config? a null would be read? WHY? constructor thinks a file has null on it? Rage face.

Say... should I make a class called SettingVal that when given a getValue() call it would say what it is?

SO:

config["Coolness"].getValue();

return 's 9001

WAIT:

How on earth would I make the getValue() method? HOW? RETURN VALUE WONT LIKE THIS!! OH CRAP!

Solution:

Another Data type comes in and checks its 'gender' ( String , Bool , Int ) and then checks it's value of that 'gender' ( strVal , boolVar , intVar )

Return values are a big problem when dealing with this. I need a stress free version , so maybe I can have a void returning method that runs another method based on what data type it is said to hold! Am I right?

I have a temporary solution, setVar works, getVar is get*Var , where * is Str , Bool or Int .

Sadly, I Haven't yet been able to properly read it from a file, the method I made to read from a file is not working. It makes a Map<String,SettingVar> , using a HashMap constructor and returns that map, but seems whenever I try to access a variable from it that variable is null . It is probably because of IOException s and FileNotFoundException s, FileNotFound ? Why? It Shouldn't be running until called. Oh, and also NullPointerException s Please Help!

SUBQUESTION: what happens when you MapVariable.put({NAME HERE}, varToPutIn) many times in a for loop? what about MapVariable.put({NAME HERE},new ...) ?

My code in links:

https://gist.github.com/anonymous/66c4d1c2d2718a4cc9b9

because I don't have enough reputation

PS: OK! ive made the config reader work now, and SettingVar , and SettingContainer and im working on ConfigWriter which is good, now working on a prototype for a java command prompt like thing, and soon a WHOLE OS!! wait... java is an os. thats why java virtual machine... oh. Well, how can I close this question and turn the outcome into a revolutionary new thingy for kids who want to learn to code java *cough cough* especialy ones with higher learning ability than social ability... and like to hang around with mature people who dont bully them like all the kids in their school. (Wow, that was specific)

Answer 1

I would use a Plain Old Java Object which you can read from JSON.

class Config {
    int coolness = 9001;
    String hello = "world";
    boolean cool = true;
}

This way you can have fields with a variety of types.

Answer 2

The type you're looking for is Map<String,Object> , but it is not type-safe and you'll have to do a bunch of casting:

Map<String,Object> config = new HashMap<>();
config.put("coolness",9001);
config.put("hello","world");
config.put("cool", true);

boolean cool     = (Boolean) config.get("cool");
String  hello    = (String)  config.get("world");
int     coolness = (Integer) config.get("coolness");

Generally, I'd recommend creating a dedicated class for holding your configuration (each field = one property), which is strongly typed and doesn't require casting, and then use something like Jackson to serialize/deserialize it from json, yaml, or xml.

This provides structure to your configuration, and will cause any issues with malformed configurations to show up when you start your application/load your configuration, and not in the middle of your application.

Answer 3

SUBQUESTION: what happens when you MapVariable.put(varToPutIn) many times in a for loop?

A Map represents a mapping. If you do this:

Map<String, Object> map = new HashMap<>();
for (int i = 0; i < 10; i++) {
    map.put("myKey", Integer.valueOf(i));
}

what happens is that you add a mapping from "myKey" to zero, then update it to one, two, three and so on. When the loop ends, "myKey" will map to nine.

In short, the map entry for "myKey" is behaving like a variable of type Integer that you assign to repeatedly.

Answer 4

I'm afraid your Gists are telling me that you simply didn't take on board what @Darth Android wrote. Rather that hashing through your code, here's a simple way to parse your config file syntax (more or less) and load it into a Map<String, Object>

Note: I have not compiled or tested this code. It is written to be read and understood, rather than borrowed.

Map<String,Object> config = new HashMap<>();
try (Scanner s = new Scanner(new FileReader(someFile))) {
    while (s.hasNext()) {

        // Syntax is '<type> <name> is <value>'

        String[] words = s.nextLine().split("\\s+");
        if (words.length != 4 || !words[2].equals("is")) {
            throw MySyntaxException("unrecognizable config");
        }
        String type = words[0];
        String name = words[1];
        String val = words[3];
        switch (type) {
        case "number":
            map.put(name,  Integer.valueOf(val));
            break;
        case "boolean":
            map.put(name,  Boolean.valueOf(val));
            break;
        case "string":
            map.put(name, val);
            break;
        default:
            throw MySyntaxException("unknown type");
        }
    } catch (NumberFormatException ex) {
        throw MySyntaxException("invalid number");
    }
}